Supramolecular biodegradable polymer

ABSTRACT

The present invention relates to a supramolecular biodegradable polymer comprising a quadruple hydrogen bonding unit (abbreviated herein as “4H-unit”), a biodegradable backbone and hard blocks and a process for preparing such a supramolecular biodegradable polymer. The supramolecular polymer is specifically suitable for biodegradable articles such as biomedical implants that need high strength and/or elasticity, e.g. medical implants in the cardio-vascular field.

FIELD OF THE INVENTION

The present invention relates to a supramolecular biodegradable polymercomprising a quadruple hydrogen bonding unit (abbreviated herein as“4H-unit”), a biodegradable backbone and hard blocks, which displaysuperior mechanical strength and elasticity while keeping its ease ofprocessing. The resulting supramolecular polymers according to theinvention are specifically suitable for biodegradable articles such asbiomedical implants that need high strength and/or elasticity, e.g.medical implants in the cardio-vascular field.

BACKGROUND OF THE INVENTION

A wide variety of biodegradable (also often designated as bioresorbableor biomedical) materials are known that are mostly based on aliphaticpolyesters (Uhrich et al., Chem. Rev. 99, 3181-3198, 1999). Themechanical properties of current biodegradable materials are stronglyrelated to their high molecular weights that are in general over 100kDa, the presence of chemical cross-links, and the presence ofcrystalline domains in these polymers. Although the crystalline domainsare beneficial for the initial high strength of the material, they dohave a strong impact on the biodegradation process of the material asthe biodegradation of crystalline domains is in general very slow andcrystalline domains may cause immunological responses. Moreover, theneed for high molecular weight polymers, in order to get the desiredmaterial properties, usually implies that high processing temperaturesare required, and these are unfavourable as thermal degradationprocesses become more likely. Additionally, the crystalline domains mayhave a negative impact on the long term elastic behaviour of thematerial due to their tendency to induce fatigue characteristics.

The present invention relates to a supramolecular biodegradable polymerthat comprises 4H-units that are capable of forming at least fourH-bridges in a row, preferably with another 4H-unit, leading to physicalinteractions between different polymer chains. The physical interactionsoriginate from multiple hydrogen bonding interactions (supramolecularinteractions) between individual 4H-units or between a 4H-unit andanother moiety capable of forming hydrogen bonds thereby formingself-complementary units, preferably comprising at least four hydrogenbonds in a row.

Units capable of forming at least four hydrogen bonds in a row, i.e.quadruple hydrogen bonding units, are in this patent applicationabbreviated as “4H-units”. Sijbesma et al. (U.S. Pat. No. 6,320,018;Science 278, 1601-1604, 1997; both incorporated by reference) discloses4H-units that are based on 2-ureido-4-pyrimidones. These2-ureido-4-pyrimidones in their turn are derived from isocytosines.

A low molecular weight telechelic polycaprolactone (PCL) end-capped with4H-units is disclosed in Dankers et al. (Polymeric Materials Sci. & Eng.88, 52, 2003; Nature Materials 4, 5688, 2005 both incorporated byreference). It was found that films of this material were biocompatiblebased on the observed attachment of fibroblast cells to the films. Thestudy on the biodegradation of this polymer showed the presence ofcrystallites, which is not favourable for bioresorption. Moreover,DSC-thermograms revealed the highly crystalline nature of the PCLbackbone. The same PCL material and PCL materials comprising several4H-units along the backbone are further characterized on theirmechanical behaviour in Dankers et al. (Biomaterials 27, 5490, 2006;incorporated by reference). This study revealed that the highlycrystalline telechelic PCL with 4H-units has a Young's modulus of about130 MPa but breaks already after about 14% elongation. Whereas, the muchless crystalline chain extended PCL-derivative with 4H-units has a lowerYoung's modulus of only about 3 MPa and an elongation of break of 576%(cf. Table 1 on page 5495). Both materials have only one melting pointabove 40° C. for the pristine non-annealed materials.

US 2009/00130172, incorporated by reference, discloses severalbiodegradable materials that comprise 4H-units mixed with bioactivemolecules comprising a 4H-unit for biomedical applications such ascoatings with controlled release of drugs. Among the materials disclosedare the materials as published by Dankers et al. mentioned above, aswell as other biodegradable polyester derivatives comprising 4H-units,notable the telechelic PCL of Dankers et al. in Example 14, and thechain extended PCL and polyadipate-based polymers with isophoronediisocyanate (IPDI) in Examples 8, 12, 13, and 15. However, all thesepolyester based materials are characterized by poor mechanicalbehaviour, either not strong enough (modulus lower than 10 MPa) or notelastic enough (elongation below 50%).

Söntjens et al. (Macromolecules 41, 5703, 2008; incorporated byreference) disclose the above mentioned polyadipate-based polymers whichare chain extended with 4H-units, as well as their analogues with1,6-hexamethylene diisocyanate (HDI). These materials are said to besuitable for biomedical applications e.g. in medical devices and tissueengineering. However, the IPDI-analogue has no thermal transition in DSCabove 40° C. whereas the HDI-analogue has only one melting point above40° C. Additionally, the materials have only a limited strength, withYoung's moduli of about 1 and about 8 MPa for the IPDI-analogue andHDI-analogue, respectively, and tensile strengths below 3 MPa.

US 2004/0087755, incorporated by reference, discloses polyurethane basedpolymers end-capped with 4H-units, alkyl diol chain extenders, and4,4′-methylene bis(phenyl isocyanate) (MDI), which can be used as hotmelt adhesive or TPU foam. These materials have limited tensilestrengths ranging from 2 to 8 MPa (Table 2) or stresses at 100%elongation between 2 to 4 MPa (Table 6). Most importantly, the aromaticMDI in these polyurethane materials hamper their possible use asbiodegradable biomedical materials, since MDI is known to result indegradation products that can comprise highly toxic aniline andderivatives thereof.

US 2012/116014, incorporated by reference, discloses a process for thepreparation of a supramolecular polymer comprising 1-50 4H-units, inwhich a 4H building block according to the formula 4H-(L-F_(i))_(r),wherein 4H represents a 4H-unit, L represents a divalent, trivalent,tetravalent or pentavalent linking group, F_(i) represents a reactivegroup, and r is 1-4, is reacted with a prepolymer comprising acomplementary reactive group, wherein the reaction mixture comprisingsaid 4H building block and said prepolymer comprises less than 10 wt. %of a non-reactive organic solvent, based on the total weight of thereaction mixture. Most preferably, r is 2 and L is a divalent C₁-C₂₀alkylene, arylene, arylalkylene or alkylarylene group, which impliesthat the 4H building block is preferably represented by the formula4H-(L-F_(i))₂. The 4H building block is preferably prepared from aprecursor of an isocytosine or a melamine derivative and a diisocyanate,wherein the diisocyanate is most preferably isophorone diisocyanate(IPDI) or methylene dicyclohexane 4,4′-diisocyanate (HMDI). Thesupramolecular polymer according to US 2012/116014 is preferably used incoating and adhesive compositions. However, supramolecular polymersobtained according to this preferred process are too stiff (high Young'smodulus) and have a low elasticity.

Hence there is a need in the art for supramolecular biodegradablematerials for biomedical applications that have a high strength and/or ahigh elasticity. Furthermore, it is desired that they can easily beprepared and processed in a biomedically acceptable way.

It is therefore an object of the present invention to provide strongsupramolecular biodegradable polymers as well as a process to preparesuch polymers. The supramolecular biodegradable polymers according tothe present invention have better material characteristics than those ofthe prior art without compromising the beneficial processing propertiesof supramolecular polymers. It is another object of the presentinvention to provide strong supramolecular biodegradable polymers usedin biomedical implants and scaffolds for tissue engineering.

SUMMARY OF THE INVENTION

The present invention relates to a supramolecular biodegradable polymercomprising structural units A, B, C and F or comprising structural unitsA, B, C and G, wherein:

structural units A are represented by divalent organic groups —P—,wherein P is a polymeric group having a M_(n) of about 250 to about50,000;

structural units B are represented by divalent organic groups —R⁵—,wherein R⁵ is selected from the group consisting of C₂-C₄₄ alkylene,C₆-C₄₄ arylene, C₇-C₄₄ alkarylene and C₇-C₄₄ arylalkylene, wherein thealkylene groups, arylene groups, alkarylene groups and arylalkylenegroups may be interrupted by 1-5 heteroatoms selected from the groupconsisting of O, N and S;structural units C are represented by divalent organic groups —R⁶—,wherein R⁶ is selected from the group consisting of C₂-C₂₀ alkylene;structural units F are independently selected from the group consistingof units according to Formulas (1), (2), (3) and (4):

structural units G are independently selected from the group consistingof terminal units according to Formulas (5) and (6):

X is N or CR¹;R¹, R³ and R⁴ are independently selected from the group consisting of:(a) hydrogen;(b) C₁-C₂₀ alkyl;R² is selected from the group consisting of C₁-C₂₀ alkylene; andwherein structural units A, B, C, F and G are bonded to each other viagroups independently selected from urethane and urea groups and whereinF and G are bonded via the 2-position by a urea moiety.

The present invention also relates to a supramolecular biodegradablepolymer that is obtainable by a process wherein:

a compound F′ independently selected from the group consisting ofFormulas (7), (8), (9) and (10), or a mixture thereof:

ora compound G′ independently selected from the group consisting ofFormulas (11) and (12), or a mixture thereof:

is reacted with:a diisocyanate compound C′ according to the Formula OCN—R⁶—NCO;a polymer A′ according to the Formula FG-P-FG; anda compound B′ according to the Formula FG-R⁵-FG;wherein:X is N or CR¹;R¹, R³ and R⁴ are independently selected from the group consisting of:(a) hydrogen;(b) C₁-C₂₀ alkyl;R² is selected from the group consisting of C₁-C₂₀ alkylene;FG is a functional group independently selected from OH and N(R¹)H;P is a polymeric group having a M_(n) of about 250 to about 50,000;R⁵ is selected from the group consisting of C₂-C₄₄ alkylene, C₆-C₄₄arylene, C₇-C₄₄ alkarylene and C₇-C₄₄ arylalkylene, wherein the alkylenegroups, arylene groups, alkarylene groups and arylalkylene groups may beinterrupted by 1-5 heteroatoms selected from the group consisting of O,N and S; andR⁶ is selected from the group consisting of C₂-C₂₀ alkylene.

The present invention further relates to biodegradable biomedicalarticles comprising the supramolecular biodegradable polymer.

DETAILED DESCRIPTION OF THE INVENTION

The verb “to comprise” as is used in this description and in the claimsand its conjugations is used in its non-limiting sense to mean thatitems following the word are included, but items not specificallymentioned are not excluded. In addition, reference to an element by theindefinite article “a” or “an” does not exclude the possibility thatmore than one of the element is present, unless the context clearlyrequires that there is one and only one of the elements. The indefinitearticle “a” or “an” thus usually means “at least one”.

(Self)-complementary units capable of forming at least four hydrogenbonds form in principle non-covalent moieties with each other. When the(self)-complementary units are capable of forming four hydrogen bonds ina row, they are used in their abbreviated form “4H-unit”. However, it iswithin the scope of this invention that the (self)-complementary units(including the 4H-units) can form non-covalent moieties with othermaterials capable of forming less than four hydrogen bonds. Unitscapable of forming at least four hydrogen bonds can form anon-self-complementary or a self-complementary binding group.Non-self-complementary means for example that a 4H-unit (I) forms abonding moiety (I)-(II) with a unit (II), wherein (II) is a different4H-unit. Self-complementary means that two 4H-units (I) form a bondingmoiety (I)-(I). It is preferred that the 4H-unit is self-complementary.The units according to Formulas (1), (2), (3) and (4) and the unitsaccording to Formulas (5) and (6) form, when incorporated in thesupramolecular biodegradable polymer according to the present invention,(self)-complementary units.

Since the term “(self)-complementary units capable of forming fourhydrogen bonds in a row is used in its abbreviated form “4H-unit”, a“supramolecular polymer comprising a (self-)complementary unit capableof forming at least four hydrogen bonds in a row” is in this documentalternatively indicated as a “supramolecular polymer comprising a4H-unit”. The 4H-unit is covalently attached to or covalentlyincorporated in the polymer chain.

The term “biodegradable” when used in this document relates tocell-mediated degradation, enzymatic degradation, hydrolytic degradationof the supramolecular biodegradable polymer and/or the biodegradablebiomedical article comprising the supramolecular biodegradable polymer.The term “biodegradable” may also relate to elimination of thesupramolecular biodegradable polymer and/or the biodegradable biomedicalarticle comprising the supramolecular biodegradable polymer from livingtissue.

In structural units F and G, the 2-position is substituted by a ureamoiety so that they form a 4H-unit as is shown below for Formula (1) andfor Formula (5):

The term “room temperature” as used in this document has its normalmeaning, i.e. that it indicates a temperature in the range of about 20°C. to about 25° C.

Molecular weights such as M_(n) are expressed as g/mol.

General Definitions

An urea moiety as indicated in this document is to be understood as amoiety according to the formula:—NR—C(X)—NR—wherein X is O or S, preferably O; and wherein R is, independently, ahydrogen atom or a linear alkyl group, preferably a hydrogen atom.

An amide moiety as indicated in this document is to be understood as amoiety according to the formula:—NR—C(X)—wherein X and R are as described above.

An urethane moiety as indicated in this document is to be understood asa moiety according to the formula:—NR—C(X)—X—wherein X and R are as described above (X can independently be O or S).

An ester moiety as indicated in this document is to be understood as amoiety according to the formula:—C(X)—X—wherein X is as described above (X can independently be O or S).

A carbonate moiety as indicated in this document is to be understood asa moiety according to the formula:—X—C(X)—X—wherein X is as described above (X can independently be O or S).

An amine moiety as indicated in this document is to be understood as amoiety according to the formula:—NR₂—wherein R is as described above.

An ether moiety as indicated in this document is to be understood as amoiety according to the formula:—X—wherein X is as described above.

An isocyanate group is to be understood as a —NCX group, wherein X is asdescribed above.

The Supramolecular Biodegradable Polymer

The supramolecular biodegradable polymer has preferably a number averagemolecular weight M_(n) of about 1,200 to about 1,000,000, morepreferably about 4,000 to about 100,000, even more preferably about8,000 to about 60,000, yet even more preferably about 10,000 to about40,000, and most preferably about 10,000 to about 30,000 Dalton.

The supramolecular biodegradable polymer may be a random polymer inwhich the structural units A, B, C and F occur in different randomsequences. The supramolecular biodegradable polymer may also be asegmented polymer in which regular sequences of A, B, C and F units canbe found as can for example schematically be shown as:—C-A-C—F—C-A-C—B—C—B—or—C—F—C-A-C—F—C—B—.

The supramolecular biodegradable polymer may also be a random polymer inwhich the structural units A, B and C occur in different randomsequences, wherein the supramolecular biodegradable polymer isend-capped with structural unit G.

In a preferred embodiment, a 9% w/v solution of the supramolecularbiodegradable polymer in a mixture of chloroform and methanol (10/1 v/v)has a dynamic viscosity at 25° C. of about 0.5 to about 10 Pa·s,preferably of about 0.8 to about 8 Pa·s, most preferably of about 0.8 toabout 5 Pa·s, as measured with a rotational viscometer.

In another preferred embodiment of this invention, the supramolecularbiodegradable polymer absorbs less than about 50% by weight of water,based on the total weight of the supramolecular biodegradable polymer,when soaked into excess of water at 25° C. for about one hour.

The supramolecular biodegradable polymer according to the presentinvention has a high mechanical strength and a high elasticity and isvery suitable for biomedical applications. Therefore, the supramolecularbiodegradable polymer according to the present invention has preferablya Young's modulus of at least 10 MPa, preferably at least 20 MPa, aneven more preferably of at least 40 MPa, as determined by standard testmethod ASTM D 1708-96 at room temperature, with a crosshead speed of 20mm/min. Preferably, the Young's modulus is lower than 150 MPa,preferably lower than 80 MPa, most preferably lower than 60 MPa.

The supramolecular biodegradable polymer according to the presentinvention has preferably also a modulus at 100% elongation of at least 5MPa, more preferably at least 10 MPa, as determined by standard testmethod ASTM D 1708-96 at room temperature, with a crosshead speed of 20mm/min. Moreover, the supramolecular biodegradable polymer is notyielding which means in this application that the modulus at 30%elongation is at least 1.0 times the modulus at 10% elongation,preferably at least 1.2 times the modulus at 10% elongation, and mostpreferably at least 1.4 times the modulus at 10% elongation, accordingto test method ASTM D 1708-96 at room temperature, with a crossheadspeed of 20 mm/min.

The supramolecular biodegradable polymer according to the presentinvention has preferably also an elongation at break of at least 100%,more preferably of at least 200%, and most preferably of at least 300%,according to standard test method ASTM D 1708-96 at room temperature,with a crosshead speed of 20 mm/min.

The supramolecular biodegradable polymer according to the presentinvention has preferably at least two thermal transitions selected froma glass transition or a melting point at a temperature between about 40°and about 140° C., more preferably between about 50° and about 130° C.

Process for Preparing the Supramolecular Biodegradable Polymer

The present invention also relates to a process for preparing thesupramolecular biodegradable polymer. In this process, a compound F′that is independently selected from the group consisting of Formulas(7), (8), (9) and (10), or a mixture thereof:

ora compound G′ that is independently selected from the group consistingof Formulas (11) and (12), or a mixture thereof:

is reacted with:a diisocyanate compound C′ according to the Formula OCN—R⁶—NCO;a polymer A′ according to the Formula FG-P-FG; anda compound B′ according to the Formula FG-R⁵-FG;wherein:X is N or CR¹;R¹, R³, and R⁴ are independently selected from the group consisting of:(a) hydrogen;(b) C₁-C₂₀ alkyl;R² is selected from the group consisting of C₁-C₂₀ alkylene;FG is a functional group independently selected from OH and N(R¹)H;P is a polymeric group having a M_(n) of about 250 to about 50,000;R⁵ is selected from the group consisting of C₂-C₄₄ alkylene, C₆-C₄₄arylene, C₇-C₄₄ alkarylene and C₇-C₄₄ arylalkylene, wherein the alkylenegroups, arylene groups, alkarylene groups and arylalkylene groups may beinterrupted by 1-5 heteroatoms selected from the group consisting of O,N and S; andR⁶ is selected from the group consisting of C₂-C₂₀ alkylene.

Accordingly, in the process according to the invention, components A′,B′, C′ and F′ or components A′, B′, C′ and G′ can be reacted as amixture. In this process, it is preferred that the ratio of the molaramounts of components A′, B′, C′ and F′ are ranging from about 1:1:3:1to 1:6:8:1, more preferably ranging from about 1:2:4:1 to 1:3:5:1, mostpreferably about 1:2:4:1, in which the molar amount of C′ is alwaysequal to about 0.8 to about 1.2 times the total molar amount of A′ plusB′ plus F′, and that the ratio of the molar amounts of components A′,B′, C′ and G′ are about ranging from about 10:10:21:2 to 20:20:41:2,more preferably ranging from about 14:14:29:2 to 18:18:37:2, mostpreferably about 16:16:33:2, in which the molar amount of C′ is alwaysequal to about 0.8 to about 1.2 times the total molar amount of A′ plusB′ plus half the molar amount of G′. However, according to the inventionit is also possible to react the components A′, B′, C′ and F′ orcomponents A′, B′, C′ and G′ in distinct steps as is explained below.These variants consisting of two or more distinct reaction steps arewithin the scope of the present invention.

It is further within the scope of the invention that the molar amountsmay differ from unity by about ±0.2, e.g. when components A′, B′, C′ andF′ are reacted as a 1:2:4:1 mixture, the molar amounts in the mixture ofcomponent A′ and component F′ may be within in the range of about 0.8 toabout 1.2, the molar amount of component B′ may be within the range ofabout 1.8 to about 2.2, and the molar amount of component C′ may bewithin the range of about 3.8 to about 4.2. Likewise, when componentsA′, B′, C′ and G′ are reacted as a 16:16:33:2 mixture, the molar amountsin the mixture of component A′ and component B′ may be within in therange of about 15.8 to about 16.2, the molar amount of component C′ maybe within the range of about 32.8 to about 33.2, and the molar amount ofcomponent G′ may be within the range of about 1.8 to about 2.2.

According to the invention, it is preferred that the molar amountsdiffer from unity by not more than about +0.1, more preferably not morethan about ±0.05.

Without being bound by theory, it is believed that the major course ofthe reactions are as schematically shown in Scheme 1 and Scheme 2,wherein components F′ according to Formulas (7)-(10) are schematicallyshown as H₂N—F″—OH (which means that in this example FG represents OH)and components G′ are schematically shown as H₂N-G″.

wherein n is such that the number average molecular weight M_(n) isabout 1,200 to about 1,000,000.

It is preferred that n is in the range of about 6 to about 20, morepreferably about 10 to about 18.

As a first preferred alternative, components A′, C′ and F′ are reactedin a first step thereby forming a prepolymer P1 and a functionalisedcomponent F′ (Scheme 1), where after prepolymer P1 and thefunctionalised component F′ and potentially unreacted C′ are reactedwith component B′ to form the supramolecular biodegradable polymer.According to this embodiment, it is preferred that prepolymer P1 andfunctionalised component F′ are reacted with component B′ wherein theratio of the molar amounts of prepolymer P1, and functionalisedcomponent F′ to component B′ is in between 1:1:1 and 1:1:6, and whereinthe molar amounts may differ from unity by about ±0.2. Likewise,components A′, C′ and G′ are reacted in a first step thereby forming aprepolymer P1 and a functionalised component G′ (Scheme 2), where afterprepolymer P1 and the functionalised component G′ are reacted withcomponent B′ to form the supramolecular biodegradable polymer whereinthe ratio of the molar amounts of prepolymer P1, and functionalisedcomponent G′ to component B′ is in between 10:10:2 and 20:20:2, andwherein the molar amounts may differ from unity by about ±0.2.

Accordingly, the present invention also relates to a process forpreparing the supramolecular biodegradable polymer, wherein:

a compound F′ that is independently selected from the group consistingof Formulas (7), (8), (9) and (10), or a mixture thereof;

ora compound G′ that is independently selected from the group consistingof Formulas (11) and (12), or a mixture thereof:

is reacted in a first step with a diisocyanate compound C′ according tothe Formula OCN—R⁶—NCO and a polymer A′ according to the Formula FG-P-FGto form a prepolymer P1 and a functionalised component F′;wherein in a second step the prepolymer P1 and the functionalisedcomponent F′ are reacted with a compound B′ according to the FormulaFG-R⁵-FG;wherein:X is N or CR¹;R¹, R³, and R⁴ are independently selected from the group consisting of:(a) hydrogen;(b) C₁-C₂₀ alkyl;R² is selected from the group consisting of C₁-C₂₀ alkylene;FG is a functional group independently selected from OH and N(R¹)H;P is a polymeric group having a M_(n) of about 250 to about 50,000;R⁵ is selected from the group consisting of C₂-C₄₄ alkylene, C₆-C₄₄arylene, C₇-C₄₄ alkarylene and C₇-C₄₄ arylalkylene, wherein the alkylenegroups, arylene groups, alkarylene groups and arylalkylene groups may beinterrupted by 1-5 heteroatoms selected from the group consisting of O,N and S; andR⁶ is selected from the group consisting of C₂-C₂₀ alkylene.

As another alternative, components A′ and C′ and components F′ and C′are reacted separately to form a prepolymer P1 and a functionalisedcomponent F′, where after prepolymer P1 and functionalised component F′are combined and reacted with 2-6 molar equivalents of component B′ andadditional 0-4 molar equivalents of C′ (Scheme 3). According to thisalternative, components A′ and C′ and components F′ and C′ are reactedin a molar ratio of preferably 1:2, respectively, wherein the molaramounts may differ from unity by about ±0.2. Prepolymer P1 andfunctionalised component F′ are then reacted with 2-6 molar equivalentsof component B′, and 0-4 molar equivalents of component C′. Again, themolar amounts may differ from unity by about ±0.2.

According to yet another alternative, component B′ is reacted withcomponent C′ to form a functionalised component B′, wherein the latteris reacted with prepolymer P1 (which is formed in a separate step) andcomponent F′ or with prepolymer P1 (which is formed in a separate step)and component G′.

According to yet another alternative, component B′ is reacted withcomponent C′ to form a functionalised component B′, wherein the latteris reacted with component A′ and functionalised component F′ (which isformed in a separate step) or with component A′ and functionalisedcomponent G′ (which is formed in a separate step).

These alternative processes are depicted in Schemes 3, 4 and 5.

Diisocyanate compound C′

The diisocyanate compound C′ has the Formula OCN—R⁶—NCO, wherein R⁶ ispreferably selected from the group consisting of cyclic, linear orbranched C₂-C₂₀ alkylene groups. More preferably, R⁶ is selected fromthe group consisting of linear C₂-C₂₀ alkylene groups, most preferablylinear C₂-C₁₆ alkylene groups.

The diisocyanate compound C′ is more preferably selected from the groupconsisting of methylene dicyclohexane 4,4-diisocyanate (HMDI),isophorone diisocyanate (IPDI), hexane diisocyanate (HDI), uretdionedimers of HDI, 1,6-diisocyanato-2,2,4-trimethylhexane and1,6-diisocyanato-2,4,4-trimethylhexane. More preferably, thediisocyanate compound C′ is hexane diisocyanate (HDI) or methylenedicyclohexane 4,4-diisocyanate (HMDI). The diisocyanate compound C′ ismost preferably hexane diisocyanate (HDI).

Polymer A′

The polymer A′ has the Formula FG-P-FG, wherein P is preferably apolymeric group having a number average molecular weight M_(n) of about250 to about 50,000, more preferably about 400 to about 20,000, evenmore preferably about 600 to about 2,500, yet even more preferably about600 to about 1,500 and most preferably about 600 to about 1,000 g/mol.

The polymer A′ is preferably telechelic. Whereas the Formula FG-P-FGindicates that polymer A′ is exactly bifunctional, in practice thistelechelic polymer can better be represented as P-(FG)_(w) wherein w mayvary within the range of about 1.8 to about 2, more preferably about 1.9to about 2 and most preferably about 1.95 to about 2.

The polymer A′ is preferably a linear polymer.

It is furthermore preferred that FG represents OH.

The polymer A′ can be selected from the group consisting ofbiodegradable polymer backbones. Most preferably, the polymer A′ ishydroxy terminated which implies that FG represents OH.

Preferably, polymer A′ is a hydrophobic polymer. Hydrophobic polymers A′are preferred in order to prevent that the biodegradation is too fast inthe aqueous environment that constitutes living tissue. According tothis invention, a hydrophobic polymer is defined as a polymer having asolubility in water at 25° C. that is lower than 10 g/L, more preferablylower than 1 g/L, and/or a polymer having a water contact angle higherthan 50° as measured at 25° C. using a static sessile drop method, morepreferably higher than 55°, and most preferably higher than 70°.

The polymer A′ is preferably selected from the group consisting ofpolyethers, polyesters, polyorthoesters, polyamides, polypeptides,polyacrylates, polymethacrylates, polycarbonates and co-polymers of suchpolymers. More preferably, the polymer A′ is selected from the groupconsisting of polyethers, polyesters, polycarbonates, polyorthoesters,polypeptides and co-polymers of such polymers. More preferably, thepolymer A′ is selected from the group consisting of polycarbonates,polyesters, polyethers and copolymers of such polymers.

In one specific embodiment of this invention, the polymer A′ is selectedfrom the group consisting of polycarbonates, polyesters, and copolymersof such polymers. Most preferably, the polymer A′ is a polyester or acopolymer of a polyester (copolyester).

In another specific embodiment of this invention, the polymer A′ isselected from the group consisting of polyethers, most preferablypolyethylene glycols.

Preferred polyesters and copolyesters are selected from polyesters andcopolyesters made by polycondensation of dicarboxylic acids and diols,by polycondensation of hydroxyacids, or by ringopening(co)polymerisation of appropriate monomers which are preferably selectedfrom the group consisting of ε-caprolactone, glycolide, (L)-lactide,(D)-lactide, 6-valerolactone, 1,4-dioxane-2-one, 1,5-dioxepan-2-one andoxepan-2,7-dione. Preferred polyesters and copolyesters are preferablypoly ε-caprolactonediols, hydroxy terminated polyadipates and hydroxyterminated polyglutarates. A preferred group of hydroxy terminatedpolyesters and copolyesters consists of poly ε-caprolactonediols,hydroxy terminated poly(1,4-butylene adipate)s, hydroxy terminatedpoly(1,2-ethylene adipate)s, hydroxy terminated poly(1,4-butyleneglutarate)s, hydroxy terminated poly(2-methyl-1,3-propylene adipate)s,hydroxy terminated poly(2-methyl-1,3-propylene glutarate)s, hydroxyterminated poly(2-methyl-1,5-pentylene adipate)s, polyesterdiols ofpolylactides, polyglycolides, poly(lactide-co-glycolide)s, poly(hydroxybutyrate)s, polyterephthalates such as polyethyleneterephthalates andpolybutyleneterephthalates, polyisophthalates, polyphthalates, andpolyesters derived from dimerised fatty acids, such as the differentPriplast grades (p.e. Priplast 3190 or Priplast 3192) marketed by Croda,UK. More preferably, the hydroxy terminated polyesters and copolyestersare selected from the group consisting of hydroxy terminated polyestersor copolyesters made by ringopening polymerisation of lactone and/orlactides, polyesters from dimerized fatty acids, poly(ε-caprolactone),poly(D,L-lactide), poly(L-lactide), or their copolyesters, even morepreferably poly(ε-caprolactone) or poly(caprolactone-co-L-lactide), mostpreferably poly(ε-caprolacton).

Polycarbonates are preferably selected from hydroxy terminatedpolycarbonates and copolycarbonates based on alkyldiol polycarbonate andpolycarbonates and copolycarbonates made by ringopening polymerizationof trimethylenecarbonate, 1,3-dioxepane-2-one, 1,3-dioxanone-2-one, and1,3,8,10-tetraoxacyclotetradecane-2,9-dione. More preferably,polycarbonates are selected from alkyldiol polycarbonate, mostpreferably 1,6-hexanediol polycarbonate.

Polyethers are preferably selected from polyethylene glycols,polypropylene glycols, poly(ethylene-co-propylene) glycols (random orblock), poly(ethylene-block-propylene-block-ethylene) glycols (alsoknown as Pluronics®), polytetramethylene glycols (i.e.poly-tetrahydrofurans) and poly(ethylene-co-tetramethylene) glycols, andtheir copolyethers. More preferably, polyethers are selected from thegroup consisting of polyethylene glycol and poly(tetrahydrofuran). Mostpreferably, the polyether is a polyethylene glycol.

Compound B′

The compound B′ has the Formula FG-R⁵-FG, wherein R⁵ is preferablyselected from the group consisting of C₂-C₄₄ alkylene, C₆-C₄₄ arylene,C₇-C₄₄ alkarylene and C₇-C₄₄ arylalkylene, wherein the alkylene groups,arylene groups, alkarylene groups and arylalkylene groups may beinterrupted by 1-5 heteroatoms selected from the group consisting of O,N and S.

Preferably, R⁵ is selected from C₂-C₄₄ alkylene, more preferably C₂-C₁₂alkylene, even more preferably C₄-C₁₂ alkylene, wherein the alkylenegroup is optionally interrupted with one or more, preferably 1-5, oxygenor nitrogen atoms.

The alkylene groups may be linear, cyclic or branched. Preferably, thealkylene group is linear.

The compound B′ has preferably a molecular weight of about 56 to about600 g/mol, more preferably a molecular weight of about 90 to about 210g/mol, most preferably a molecular weight of about 100 to about 180g/mol.

Preferably, the compound B′ is a diol, more preferably a linear C₂-C₂₀alkyl α,ω-diol, wherein the alkylene group is optionally interruptedwith one or more, preferably 1-5, oxygen atoms. Even more preferably thecompound B′ is selected from diethylene glycol, triethyleneglycol, and1,6-hexanediol. Most preferably, the compound B′ is 1,6-hexanediol.

The Process

The process for the preparation of the supramolecular biodegradablepolymer according to this invention can be done by any method known inthe art, for example in solution or in the bulk using reactiveextrusion. The process is preferably performed at a temperature betweenabout 10° C. and about 140° C., more preferably between about 20° C. andabout 120° C., and most preferably between about 40° C. and about 90° C.

The process for the preparation of the supramolecular biodegradablepolymer may be performed in the presence of a catalyst. Examples ofsuitable catalysts are known in the art and they promote the reactionbetween isocyanates and hydroxyl groups. Preferred catalysts includetertiary amines and catalysts comprising a metal. Preferred tertiaryamines are 1,4-diazabicyclo[2.2.2]octane (DABCO) and1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Preferred catalysts comprisinga metal are tin(IV) compounds and zirconium(IV) compounds, preferablyselected from the group consisting of tin(II)octanoate,dibutyltin(IV)laurate and zirconium(IV)acetoacetate. Most preferably,the catalyst is tin(II)octanoate. The amount of catalyst is generallybelow about 1% by weight, preferably below about 0.2% by weight and mostpreferably below about 0.03% by weight, based on the total amount ofreactants.

In a preferred embodiment of this invention, the process is performed inthe presence of a non-reactive organic solvent, wherein it is preferredthat the amount of the non-reactive organic solvent is at least about 20weight %, more preferably at least about 40 weight %, even morepreferably at least about 60 weight %, and most preferably at leastabout 70 weight %, based on the total weight of the reaction mixture. Itis also preferred that the reaction mixture does not comprise anyinorganic solvents such as water. Non-reactive solvents are preferablyselected from non-protic polar organic solvents, preferablytetrahydrofuran, dioxane, N-methylpyrollidone, dimethylformamide,dimethylacetamide, dimethyl sulfoxide, propylene carbonate, ethylenecarbonate, 2-methoxy-ethyl-acetate. Most preferably, the non-reactivesolvent is dimethyl sulfoxide or propylene carbonate.

The supramolecular biodegradable polymer can be isolated as such, or canbe isolated as a powder after precipitation in a non solvent, choppedinto pellets, spun in fibers, extruded into films, directly dissolved ina medium of choice, or transformed or formulated into whatever form thatis desired.

Preferably, the supramolecular biodegradable polymer is molten andmelt-spun, extruded with fused deposition modelling, processed withanother 3D printing techniques such as laser sintering, or dissolved ina volatile organic solvent and electrospun, in order to obtain ascaffold for tissue engineering. Said scaffold may comprise woven ornon-woven fibers. Most preferably, the supramolecular biodegradablepolymer is electrospun from solution into a scaffold for tissueengineering comprising non-woven fibers.

Applications

The supramolecular biodegradable polymers according to the invention arepreferably suitable for manufacturing biomedical articles, in particularmedical implants, scaffolds for tissue engineering, in which human oranimal tissue is grown on a substrate, scaffolds for cardio-vascularapplications, such as artificial heart valves or vascular grafts, orligaments reconstructions, but are not limited thereto (they could alsobe all kinds of scaffolds used for other organs/devices/objects).

EXAMPLES

The following examples further illustrate the preferred embodiments ofthe invention. When not specifically mentioned, chemicals are obtainedfrom Aldrich.

Example 1: Preparation of UPy-Monomer A

2-Acetylbutyrolactone (2.38 g, 19 mmol) and guanidine carbonate (3.3 g,37 mmol) were put to reflux in absolute ethanol (20 mL) in the presenceof triethylamine (5.2 mL). The solution became yellow and turbid. Afterovernight heating at reflux, the solid was filtered, washed withethanol, and suspended in water. The pH was adjusted to a value of 6-7with an HCl-solution, and the mixture was stirred for a while.Filtration, rinsing of the residue with water and ethanol and subsequentdrying of the solid gave the pure UPy-monomer A. ¹H NMR (400 MHz,DMSO-D): δ 11.2 (1H), 6.6 (2H), 4.5 (1H), 3.4 (2H), 2.5 (2H), 2.1 (3H).FT-IR (neat): ν (cm⁻¹) 3333, □3073, 2871, 1639, 1609, 1541, 1487, 1393,1233, 1051, 915, 853, 789, 716.

Example 2: Preparation of UPy-Monomer B

UPy-monomer A (1 g, 5.9 mmol) was suspended in 1,6-hexyldiisocyanate (12mL, 75 mmol) and pyridine (1 mL) and was stirred at 90° C. A clearsolution developed, and thereafter some gel particles formed (unwanted).The solution was cooled and filtered through some celite. The filtratewas dropped into pentane giving a white precipitate. This precipitatewas again stirred in pentane to remove the last traces of1,6-hexyldiisocyanate. Isolation via filtration was followed by drying,giving the pure diisocyanate. ¹H NMR (400 MHz, CDCl₃): δ 13.1 (1H), 11.9(1H), 10.2 (1H), 4.8-4.6 (1H), 4.2 (2H), 3.3 (6H), 3.1 (2H), 2.7 (2H),2.3 (3H), 1.7-1.2 (16H). FT-IR (neat): ν (cm⁻¹) 3314, □2936, 2263, 1688,1662, 1640, 1590, 1535, 1444, 1257, 1140, 1025, 780, 742.

Example 3: Preparation of Polymer 1

Telechelic hydroxy terminated polycaprolacton with a molecular weight of1250 Da (20.4 g, 16.3 mmol, dried in vacuo), UPy-monomer B (8.24 g, 16.3mmol), hexamethylene diisocyanate (5.48 g, 32.6 mmol) and one drop oftin dioctoate were dissolved in dry DMSO (60 mL) and stirred at 80° C.The next day, 1,6-hexanediol (3.85 g, 32.6 mmol, dried in vacuo) wasadded to the reaction mixture, followed by stirring for another 2 hoursat 80° C. The reaction mixture was cooled to 25° C. and its viscositywas lowered by the addition of additional DMSO in order to precipitatethe mixture in water. The polymer was collected as a white elasticsolid, redissolved in chloroform/methanol (7/3 v/v) and repriciptated inan excess of methanol. This resulted in a clear elastic solid afterdrying in vacuo at 50° C. SEC (THF, PS-standards): M_(n)=14.6 kDa,D=1.8.

Example 4: Preparation of Polymer 2

Telechelic hydroxy terminated polycaprolacton with a molecular weight of2000 Da (40.8 g, 20.4 mmol, dried in vacuo) and hexamethylenediisocyanate (13.7 g, 81.6 mmol) were stirred together at 80° C. in thepresence of one drop of tin dioctoate for 2 hours. To this reactionmixture was subsequently added UPy-monomer A (3.45 g, 20.4 mmol)dissolved in dry DMSO (120 mL) and stirred overnight at 80° C. The nextday, 1,6-hexanediol (4.81 g, 40.8 mmol, dried in vacuo) was added to thereaction mixture, followed by stirring for another 2 hours at 80° C. Thereaction mixture was cooled to 25° C. and its viscosity was lowered bythe addition of additional DMSO in order to precipitate the mixture inwater. The polymer was collected as a white elastic solid, redissolvedin chloroform/methanol (7/3 v/v) and reprecipitated in an excessmethanol. This resulted in a clear elastic solid after drying in vacuoat 50° C. SEC (THF, PS-standards): M_(n)=26 kD, D=1.4.

Example 5: Preparation of Polymer 3

Telechelic hydroxy terminated polycaprolacton with a molecular weight of2000 Da (40.0 g, 20 mmol, dried in vacuo) and hexamethylene diisocyanate(16.5 g, 98 mmol) were stirred together at 80° C. in the presence of onedrop of tin dioctoate for 2 hours. To this reaction mixture wassubsequently added UPy-monomer A (3.38 g, 20 mmol) dissolved in dry DMSO(120 mL) and stirred overnight at 80° C. The next day, 1,6-hexanediol(7.08 g, 60 mmol, dried in vacuo) was added to the reaction mixture,followed by stirring for another 2 hours at 80° C. The reaction mixturewas cooled to 25° C. and its viscosity was lowered by the addition ofadditional DMSO in order to precipitate the mixture in water. Thepolymer was collected as white elastic solid, redissolved inchloroform/methanol (7/3 v/v) and reprecipitated in an excess methanol.This resulted in a clear elastic solid after drying in vacuo at 50° C.SEC (THF, PS-standards): M_(n)=21 kDa, D=1.5.

Example 6: Preparation of Polymer 4

Telechelic hydroxy terminated polycaprolacton with a molecular weight of800 Da (40.0 g, 50 mmol, dried in vacuo), 1,6-hexanediol (11.7 g, 99mmol), and UPy-monomer A (8.36 g, 49 mmol) were dissolved in dry DMSO(120 mL) at 80° C. To this reaction mixture was added hexamethylenediisocyanate (32.6 g, 19 mmol) while stirring, followed by the additionof one drop of tin dioctoate. This reaction mixture was stirredovernight at 80° C. The next day, the reaction mixture was cooled to 25°C. and its viscosity was lowered by the addition of additional DMSO inorder to precipitate the mixture in water. The polymer was collected aswhite elastic solid, redissolved in chloroform/methanol (7/3 v/v) andreprecipitated in an excess methanol. This resulted in a clear elasticsolid after drying in vacuo at 50° C. SEC (THF, PS-standards): M_(n)=16kDa, D=1.4.

Example 7: Preparation of Polymer 5

Telechelic hydroxy terminated poly(ethylene glycol) with a molecularweight of 3 kDa (20 gram, 6.67 mmol) was dried at 120° C. in vacuo for 2hours. Subsequently, UPy-monomer A (1.13 gram, 6.67 mmol),hexanediisocyanate (4.13 gram, 24.6 mmol), 50 mL dimethylformamide andone drop of dibutyltindilaurate were added to the polymer. The reactionmixture was stirred at 90° C. After one hour, 1,6-hexanediol (1.56 gram,13.3 mmol) was added. The reaction mixture was stirred for 8 hours at90° C. Subsequently, the reaction mixture was diluted with 50 mL ofmethanol and poured into 500 mL of diethylether. The precipitatedpolymer was dissolved into 70 mL chloroform and 70 mL methanol andpoured into 500 mL diethylether. The precipitated polymer was dried invacuo and obtained as a white solid. SEC (DMF/LiBr, PS-standards):M_(n)=27 kDa, D=3.0.

Example 8: Preparation of Polymer 6

Telechelic hydroxy terminated poly(ethylene glycol) with a molecularweight of 10 kDa (20 gram, 2 mmol) was dried at 120° C. in vacuo for 2hours. Subsequently, UPy-monomer A (0.34 gram, 2 mmol),hexanediisocyanate (1.24 gram, 7.38 mmol), 50 mL dimethylformamide andone drop of dibutyltindilaurate were added to the polymer. The reactionmixture was stirred at 90° C. After one hour, 1,6-hexanediol (0.47 gram,4 mmol) was added. The reaction mixture was stirred for 8 hours at 90°C. Subsequently, the reaction mixture was diluted with 50 mL of methanoland poured into 500 mL of diethylether. The precipitated polymer wasdissolved into 70 mL chloroform and 70 mL methanol and poured into 500mL diethylether. The precipitated polymer was dried in vacuo andobtained as a white solid. SEC (DMF/LiBr, PS-standards): M_(n)=55 kDa,D=1.9.

Comparative Example 1: Preparation of Polymer C1

Telechelic hydroxy terminated polycaprolacton with a molecular weight of2000 Da (73.0 g, 37 mmol, dried in vacuo) was stirred together withUPy-monomer A (5.29 g, 31 mmol) at 60° C. To this reaction mixture wasadded isophoronene diisocyanate (16.2 g, 73 mmol) anddibutyltindilaurate (15 mg) while stirring, followed by stirring thereaction mixture for 8 hours at 80° C. and subsequent 1.5 hours at 120°C. Subsequent the reaction mixture was put in an oven at 150° C. for 1hour, followed by cooling to 25° C. and soaking the polymer in ethanolovernight. The polymer was dried in vacuo at 50° C., resulting in atough opaque material. SEC (THF, PS-standards): M_(n)=14.6 kDa, D=1.8.

Comparative Example 2: Preparation of Polymer C2

Telechelic hydroxy terminated polycaprolacton with a molecular weight of2100 Da (25.0 g, 12 mmol, dried in vacuo) was dissolved in drychloroform (750 mL) after which2(6-isocyanatohexylaminocarbonylamino)-6-methyl-4[1H]pyrimidinone (8.8g, 30 mmol, obtained according to Folmer et al., Adv. Mater. 12, 874,2012) was added. After addition of one drop of dibutyltindilaurate thesolution was refluxed for 16 hours. Then 5 gram silica kieselgel 60 wereadded and the mixture was refluxed for another 8 hours. After dilutionof the mixture with chloroform, the silica was removed by filtrationusing hyflo. The solution was concentrated under reduced pressure. Thematerial was precipitated from chloroform in hexane and filtrated. Theresulting material was dried for 24 hours in vacuo resulting in a whitefluffy material. SEC (THF, PS-standards): M_(n)=1.7 kDa, D=1.3.

Comparative Example 3: Preparation of Polymer C3

Comparative Example 3 is similar to Example 4, wherein instead ofhexamethylene diisocyanate (HDI), isophoron diisocyanate (IPDI) wasused.

Telechelic hydroxy terminated polycaprolacton with a molecular weight of808 Da (10.0 g, 12.4 mmol), 1,6-hexanediol (2.92 g, 24.8 mmol) andUPy-monomer A (2.09 g, 12.4 mmol) were dissolved in dry DMSO (10 mL) at80° C. To this reaction mixture was added isophoron diisocyanate (11.34g, 51 mmol) while stirring, followed by the addition of two drops of tinoctoate. This reaction mixture was stirred overnight at 80° C. The nextday, the viscosity of the reaction mixture was lowered by the additionof additional DMSO in order to precipitate the mixture in water. Thepolymer was collected as a white elastic solid, redissolved inchloroform/methanol (7/3 v/v) and reprecipitated in an excess methanol.The precipitated polymer was dried in vacuo and obtained as a cleartough solid. SEC (DMF, PEG-standards): 14 kDa, D=1.9.

Comparative Example 4: Preparation of Polymer C4

Comparative Example 4 is similar to Example 4, wherein instead ofhexamethylene diisocyanate (HDI), methylene dicyclohexane4,4′-diisocyanate (HMDI) was used.

Telechelic hydroxy terminated polycaprolacton with a molecular weight of808 Da (10.0 g, 12.4 mmol), 1,6-hexanediol (2.92 g, 24.8 mmol) andUPy-monomer A (2.09 g, 12.4 mmol) were dissolved in dry DMSO (10 mL) at80° C. To this reaction mixture was added methylene dicyclohexane4,4′-diisocyanate (HMDI) (13.38 g, 51 mmol) while stirring, followed bythe addition of two drops of tin octoate. This reaction mixture wasstirred overnight at 80° C. The next day, the viscosity of the reactionmixture was lowered by the addition of additional DMSO in order toprecipitate the mixture in water. The polymer was collected as whiteelastic solid, redissolved in chloroform/methanol (7/3 v/v) andreprecipitated in an excess methanol. The precipitated polymer was driedin vacuo and obtained as a clear tough solid. SEC (DMF, PEG-standards):13 kDa, D=1.9.

Example 9: Thermal and Mechanical Properties

The following tables show the superior thermal and mechanical propertiesof the polymers according to this invention when compared to the stateof the art.

TABLE 1 Thermal transitions of the Polymers of the Examples above 40° C.Polymer No T_(g) (° C.) T_(m1) (° C.) T_(m2) (° C.) 1 —  50  93 2 —  53116 3 —  59 126 4 52 111 — C1 —  47 — C2 —  43  60 C3 — — — C4 62 — —

Thermal data were obtained using Differential Scanning Calorimetry (DSC)with a heating rate of 20° C./min and a heating range from −80° C. to160° C. Data are based on the first heating runs.

TABLE 2 Mechanical data of the Polymers of the Examples Tensile PolymerE_(mod) E_(10%) E_(30%) E_(100%) strength Elongation No (MPa) (MPa)(MPa) (MPa) (MPa) at break 1 37 2.3 3.8 4.7 8.0 470% 2 30 2.1 3.6 5.7 16500% 3 80 3.6 5.0 7.0 11 250% 4 77 6.5 9.3 12 21 320% C1 253 11.2 11.28.2 10 470% C2 49 2.4 2.4 fails 3.8  27% C3 360 16.6 16.3 21.4 44.9 210%C4 420 22.0 20.9 27.8 45.2 265%

Tensile testing was performed on dog bones cut from solvent casted filmsaccording to ASTM D1708-96 specifications in air at room temperaturewith an elongation rate of 20 mm/min with a preload of 0.02 N.

TABLE 3 Dynamic viscosity of the Polymers of the Examples in solutionPolymer No Viscosity (Pa · s) 3 0.84 4 4.04 C1 0.16 C2 0.05 C3 6.8  C434.7 

Viscosity testing was performed on the polymers dissolved inchloroform/methanol mixtures (10/1 v/v) at 9% weight per volume at 25°C., with a Haake Viscotester 550 equipped with a FL1000 immersionspindle.

Examples of Processing of the Bioresorbable Supramolecular Material

Example 10—Melt Spinning

Polymer 2 of Example 4 was melt spun using by collecting the moltenextruded polymer on a rotating drum. This resulted in the formation oflong fibres which can be further processed into mats or other wovenstructures applicable as scaffold for tissue engineering. Extrusion wasperformed at 140° C. and 90 rpm with a Haake Minilab extruder equippedco-rotating screws and a 0.2 mm die.

Example 11—Electro Spinning

Polymer 3 of Example 5 was dissolved in chloroform/ethanol (95/5) with aconcentration of 10 wt %. The resulting solution had a viscosity highenough to allow stable electro-spinning of the solution with the desiredfibre thicknesses. The resulting non-wovens can be further used asscaffold materials for tissue engineering. Electro-spinning wasperformed at 18 kV, 0.05 mL/min, and 15 cm distance.

The invention claimed is:
 1. A process for preparing a supramolecularbiodegradable polymer for medical implants or scaffolds forcardiovascular applications wherein: a compound F′ that is independentlyselected from the group consisting of Formulas (7), (8), (9) and (10),or a mixture thereof:

is reacted with: a diisocyanate compound C′ according to the FormulaOCN—R⁶—NCO; a polymer A′ according to the Formula HO—P—OH that isselected from hydroxy terminated polyethylene glycols, hydroxyterminated polypropylene glycols, hydroxy terminatedpoly(ethylene-co-propylene) glycols, hydroxy terminatedpoly(ethylene-block-propylene-block-ethylene) glycols, and hydroxyterminated poly(ethylene-co-tetramethylene) glycols; and a compound B′according to the Formula HO—R⁵—OH having a molecular weight of about 56to about 210 g/mol; in the presence of a non-reactive non-protic polarorganic solvent selected from the group consisting of dioxane,N-methylpyrollidone, dimethyl formamide, dimethylacetamide, dimethylsulfoxide, propylene carbonate, ethylene carbonate and2-methoxyethyl-acetate, wherein the compounds F′, C′, B′, polymer A′ andthe non-reactive non-protic polar organic solvent together form areaction mixture, and wherein the amount of the non-reactive non-proticpolar organic solvent is at least 20 weight %, based on the total weightof the reaction mixture, wherein: X is N or CR¹; R¹ is selected from thegroup consisting of: (a) hydrogen; (b) C₁-C₂₀ alkyl; R² is selected fromthe group consisting of C₁-C₂₀alkylene; FG is a functional groupindependently selected from OH and N(R¹)H; P is a polymeric group havinga M_(n) of about 400 to about 20,000; R⁵ is selected from the groupconsisting of linear C₂-C₁₂ alkylene groups, wherein the alkylene groupsare optionally interrupted by 1-5 heteroatoms selected from the groupconsisting of O, N and S; and R⁶ is selected from the group consistingof linear C₂-C₁₆ alkylene groups.
 2. The process according to claim 1,wherein the supramolecular biodegradable polymer has a number averagemolecular weight M_(n) of about 1,200 to about 1,000,000.
 3. The processaccording to claim 1, wherein A′, B′, C′ and F′ are reacted in a molarratio of 1:1:3:1 to 1:6:8:1, in which the molar amount of C′ is alwaysequal to 0.8 to 1.2 times the total molar amount of A′ plus B′ plus F′.4. The process according to claim 1, wherein FG is OH.
 5. The processaccording to claim 1, wherein compound C′ according to FormulaOCN—R⁶—NCO is 1,6-hexane diisocyanate.
 6. The process according to claim1, wherein polymer A′ is a hydroxy terminated polyethylene glycol,polypropylene glycol, or poly(ethylene-block-propylene-block-ethylene)glycol.
 7. The process according to claim 1, wherein compound B′according to formula HO—R⁵—OH is 1,6-hexane diol.
 8. The processaccording to claim 1, wherein compound F′ is according to Formula (7).9. The process according to claim 1, wherein P is a polymeric grouphaving a M_(n) of about 600 to about 2,500.
 10. A supramolecularbiodegradable polymer for medical implants or scaffolds forcardiovascular applications, said supramolecular biodegradable polymerhaving a modulus at 30% elongation that is at least 1.2 times themodulus at 10% elongation according to test method ASTM D 1708-96 atroom temperature with a crosshead speed of 20 mm/min, the supramolecularbiodegradable polymer comprising structural units A, B, C and F,wherein: structural units A are represented by divalent organic groups—P—, wherein P is a polymeric group having a M_(n) of about 400 to about20,000 and wherein structural units A are selected from polyethyleneglycol, polypropylene glycol, poly(ethylene-co-propylene glycol),poly(ethylene-block-propylene-block-ethylene) glycol, andpoly(ethylene-co-tetramethylene) glycol units; structural units B arerepresented by divalent organic groups —R⁵—, wherein R⁵ is selected fromthe group consisting of C₂-C₁₂ alkylene, which are optionallyinterrupted by 1-5 heteroatoms selected from the group consisting of O,N and S; structural units C are represented by divalent organic groups—R⁶—, wherein R⁶ is —(CH₂)₆—; structural units F are independentlyselected from the group consisting of units according to Formulas (1),(2), (3) and (4):

X is N or CR¹; R¹ is selected from the group consisting of: (a)hydrogen; (b) C₁-C₂₀ alkyl; R² is selected from the group consisting ofC₁-C₂₀ alkylene; and wherein structural units C and F are bonded to eachother via groups independently selected from urethane and urea groups,wherein structural units A and B are bonded to other structural unitsvia urethane groups only and wherein F is bonded via the 2-position ofthe pyrimidine moiety or via the 2-position of the triazine moiety by aurea moiety.
 11. The supramolecular biodegradable polymer according toclaim 10, wherein structural units A are polyethylene glycol,polypropylene glycol, or poly(ethylene-block-propylene-block-ethylene)glycol units.
 12. The supramolecular biodegradable polymer according toclaim 10, wherein R⁵ is —(CH₂)₆—.
 13. The supramolecular biodegradablepolymer according to claim 10, wherein structural unit F is according toFormula (1).
 14. The supramolecular biodegradable polymer according toclaim 10, wherein P is a polymeric group having a M_(n) of about 600 toabout 2,500.
 15. A medical implant or scaffold for cardiovascularapplications comprising a supramolecular biodegradable polymer accordingto claim
 10. 16. The scaffold according to claim 15, wherein thescaffold is a heart valve or a vascular graft.